Such piston rod supports are known in pneumatic and hydraulic working cylinders, in which the piston and with it the piston rod are moved back and forth by suitably loading the piston with a pneumatic or hydraulic working medium. Said movement is often used to drive an article which is fixedly connected to the outer end of the piston rod. In this case one obtains for the unit which is formed by the piston and the piston rod a so-called three-point bearing, since the piston is guided in the cylinder and the piston rod is guided in the cylinder head and in addition the piston rod is secured on the article to be driven. This three-point bearing represents a redundancy in guidance, which in previous working cylinders, in which the piston rod is supported rigidly in the cylinder head, leads to considerable disadvantages.
If for example the axis of the movement of the driven article does not exactly coincide with the cylinder axis, the piston rod is slightly tilted during its back and forth movement, which results in a canting of the piston rod in the area of the bearing bushing. This results in increased friction, which produces not only wear of the bearing bushing, but also an energy loss. This friction also brings about, particularly at low speeds, a suddenly occurring, or jerky, movement of the piston rod.
Therefore, the basic purpose of the present invention is to produce a piston rod support, in which a canting of the piston rod on the bearing bushing is avoided.
This purpose is attained inventively by arranging a sleeve of elastic material between the bearing bushing and the wall of the through opening, which elastic sleeve encloses the bearing bushing.
In this manner one obtains so to speak a floating support of the bearing bushing and thus also of the piston rod in the through opening, so that the piston rod tilts as permitted by an elastic deformation of the elastic sleeve and can be adjusted to the axis of movement of the driven article, without canting of the piston rod with respect to the bearing bushing.
Advantageously, the sleeve projects axially beyond both sides of the bearing bushing, wherein the two projecting end sections of the sleeve are constructed as seals which rest on the piston rod. Thus in this exemplary embodiment the sleeve serves not only for supporting the bearing bushing, but it forms also an inner and outer seal, of which the outer seal serves, aside from its sealing action, also to wipe off dirt particles from the piston rod.
The two end sections of the sleeve can radially grip over the ends of the bearing bushing, wherein the two end sections of the sleeve together with the center sleeve section, which extends between them, define a recess which receives the bearing bushing, so that the bearing bushing is also held securely in axial direction by the sleeve.
If the bearing bushing is held in a snap fit in the recess, the bearing bushing can be inserted simply and yet permanently into the sleeve. In this case it is also possible, depending on use conditions, to insert bearing bushings of different material into the same sleeve. If necessary it is also possible to easily take apart the sleeve and the bearing bushing, so that for example a worn sleeve can be replaced without replacing the bearing bushing.
A further advantageous measure consists in the two end sections of the sleeve being constructed as lip seals, in which each end section has a leg forming a sealing lip, which leg is directed away from the bearing sleeve and extends slightly inclined inwardly toward the piston rod.